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1. Introduction
First generation monocrystalline and multicrystalline silicon technology still dominates the photovoltaic (PV) industry with a market share of over 90% due to high energy conversion efficiencies, constant price reduction and proven long-term reliability [Cui et al., 2022; National Renewable Energy Laboratory (NREL), 2020]. In PV manufacturing, 180 μm-thick crystalline silicon (cSi) wafers are used for fabrication of solar cells (Zhu et al., 2022). To date, the module price for monocrystalline (mono cSi) technology has reduced to less than US$0.25/Wattp [International Technology Roadmap for Photovoltaic (ITRPV), 2021]. The module price can be reduced further if the thickness of the cSi wafers in the solar cells can be reduced to below 100 μm. Besides, reducing the thickness to below 100 μm makes the wafers flexible, which enables integration of the solar cells on curved surfaces. However, the thickness reduction leads to efficiency penalty, as thinner wafers result in incomplete light absorption, leading to lower photogeneration in the solar cells (Durmaz et al., 2021; Um et al., 2021). To retain broadband light absorption in the thinner cSi wafers, effective light management techniques have to be used in the solar cells (Hwang et al., 2018).
Black silicon (bSi) has a great potential in solar cell applications, as it provides superior broadband absorption from ultraviolet until infrared regions (Fan et al., 2021; Jia et al., 2017). Various methods have been used in the literature to fabricate flexible bSi wafers (with thickness of less than 100 μm), including metal-catalyzed chemical etching (MCCE), femtosecond laser irradiation and electrochemical etching (Arafat et al., 2021; Chai et al., 2020). MCCE is usually embraced, as it is simple and involves a low-cost process (Alhmoud et al., 2021). After the MCCE process, random nanotextures, known as bSi, are formed on the wafer surface which suppress reflection by providing a graded refractive index (n) transition, leading to increased light absorption and an enhancement of the photocurrent of the flexible cells (Chai et al., 2020; Lu and Barron, 2013). Reducing the bSi wafer thickness less than 100 μm compromises light absorption for the wavelengths longer than 800 nm. Furthermore, the flexible bSi wafers are brittle and fragile in nature, therefore easily broken. To address these challenges, the flexible...